Vulnerability in firefox-esr (DEBIAN-CVE-2026-8091)

Summary

Vulnerability in firefox-esr (DEBIAN-CVE-2026-8091). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 140.10.1esr-1~deb11u1 or later.

Original description

The description as published by the source.

Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 150, Thunderbird 150, Firefox ESR 140.10.1, Thunderbird 140.10.1, and Firefox ESR 115.35.2.

Source: OSV.dev (Open Source Vulnerabilities) OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as DEBIAN-CVE-2026-8091 has been found in firefox-esr.
Successful exploitation can lead to full system takeover.
What to do: upgrade firefox-esr to 140.10.1esr-1~deb11u1 or later.
If unsure, ask your IT team or search "firefox-esr DEBIAN-CVE-2026-8091" on the vendor's site.

DEBIAN-CVE-2026-8091 (firefox-esr)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 140.10.1esr-1~deb11u1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in firefox-esr.

📍 Affected scope

Check the vendor advisory for the affected versions of firefox-esr.

🔥 Severity

Severity: ?. Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 140.10.1esr-1~deb11u1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'firefox-esr' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'firefox-esr' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で firefox-esr を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade firefox-esr to 140.10.1esr-1~deb11u1
```
ステージング環境で 140.10.1esr-1~deb11u1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Debian:11 firefox-esr

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"140.10.1esr-1~deb11u1"}]}]

Debian:12 firefox-esr

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"140.10.1esr-1~deb12u1"}]}]

Debian:13 firefox-esr

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"140.10.1esr-1~deb13u1"}]}]

Debian:14 firefox-esr

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"140.10.1esr-1"}]}]

Debian:11 thunderbird

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:140.10.1esr-1~deb11u1"}]}]

Debian:12 thunderbird

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:140.10.1esr-1~deb12u1"}]}]

Debian:13 thunderbird

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:140.10.1esr-1~deb13u1"}]}]

Debian:14 thunderbird

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:140.10.1esr-1"}]}]

References

advisory security-tracker.debian.org